1. Field of the Invention
The present invention relates to a monolithic ceramic electronic component. In particular, the present invention relates to a monolithic ceramic electronic component including a ceramic sintered body including a plurality of first and second inner electrodes that are alternately disposed inside the ceramic sintered body to be opposed to each other with a ceramic layer interposed between the adjacent first and second inner electrodes.
2. Description of the Related Art
Monolithic ceramic electronic components, e.g., monolithic ceramic capacitors, have been used in many electronic devices, such as cellular phones and notebook personal computers.
A trend toward smaller sizes and larger capacities of monolithic ceramic capacitors has recently increased. Even in power supply circuits, for example, in which aluminum electrolytic capacitors and tantalum capacitors have been primarily used to date, monolithic ceramic capacitors having a large capacity of 10 μF to 100 μF have recently been used. Generally, an electrostatic capacity is proportional to the relative dielectric constant, the area in which inner electrodes are opposed to each other, and the number of stacked inner electrodes, while it is inversely proportional to the thickness of a dielectric layer. Therefore, various proposals have been made to obtain a larger electrostatic capacity while maintaining predetermined dimensions. In the monolithic ceramic capacitor having a large capacity, the thickness of the dielectric layer is reduced to 1 μm or less, and thus, a dielectric material, such as barium titanate, is required to have a grain size of 1 μm or less while maintaining high crystallinity. Further, the number of stacked inner electrodes is as high as 1000 in some cases, and a smooth electrode having a high coverage is required. In addition, the ceramic layers and the inner electrodes are integrally sintered into a monolithic structure in a manufacturing process. At that time, internal stress generated upon expansion and shrinkage during the sintering must be reduced in order to prevent structural defects.
In such a situation, monolithic ceramic electronic components, in which defects after firing, such as cracks and delamination, are avoided even when the thickness of the ceramic green sheets and the inner electrodes are reduced and a large number of layers are stacked, and methods of manufacturing them are described in the Japanese Unexamined Patent Application Publication No. 2003-318060, for example.
One example of methods for improving the performance of a monolithic ceramic electronic component is to develop a ceramic material having higher performance. However, a large amount of time and efforts are required to develop the ceramic material having higher performance.
Another example of methods for improving the performance of a monolithic ceramic electronic component is to reduce the thickness of each ceramic layer, to increase the number of stacked ceramic layers, and to increase an area where inner electrodes are opposed to each other.
When attempting to reduce a gap portion in which the inner electrodes are not disposed, so as to increase the area in which inner electrodes are opposed to each other, humidity resistance cannot be obtained at a sufficiently high level in some cases. In other words, there has been a problem in that it is difficult to obtain high performance and high humidity resistance.